The introduction of interventional devices into a given arterial or venous blood vessel for a variety of purposes, such as for performing percutaneous transluminal coronary angioplasty (PTCA) or for delivering and implanting a stent or stent graft, is well known in the art. Several techniques for introducing such catheters are available, including the Seldinger technique. Broadly described the Seldinger technique involves surgically opening a vein or artery with a needle, inserting a guidewire into the vein or artery through the lumen of the needle, withdrawing the needle, inserting over the guidewire a dilator located inside an associated sheath introducer having a hemostasis valve, removing the dilator and guidewire, and inserting a catheter through the hemostasis valve and sheath into the blood vessel. During this process, care must be exercised to prevent introduction of air into the vessel and to avoid leakage of blood from a proximal end of the sheath introducer. To avoid the risk of both air embolism and blood contamination of the clinician, conventional introducers employ various types of hemostasis valves having a single proximal input port that is designed for use with catheters and guidewires that have various diameters.
In interventional procedures where it may be necessary to utilize different interventional devices, such as procedures for percutaneously delivering and implanting endovascular grafts for treatment of certain types of abdominal aortic aneurysms, a sheath introducer with a hemostasis valve having a single proximal input port may not ensure hemostasis of each interventional device in use during the procedure. In such cases, a clinician may utilize a puncturable hemostasis valve that can be adapted to achieve modest hemostasis of various devices to introduce additional device(s), although hemostasis is generally very poor with this practice. As such a need exists in the art for a sheath introducer that ensures hemostasis during treatments that require the introduction and manipulation of various catheters or other interventional devices.
Therefore, the prior art has addressed many configurations of hemostasis valves attempting to provide an adequate seal by a gasket at low and relatively higher blood pressure conditions for both air and blood while accommodating the wide range of diameters of devices inserted through the introducer sheath. Prior art hemostasis valves have, in many instances, been of the gasket sealing type, such as those shown in U.S. Pat. Nos. 4,000,739, 4,424,833, and 4,909,798, which comprise a pin hole and a Y-shaped slit, back-to-back gasket assembly in either one or two-piece parts. The first, doughnut-shaped, gasket is provided with a hole slightly smaller than the diameter of the catheter to be inserted, while the second gasket is provided with a Y-shaped slit. When guide wires or catheters which are too small in diameter are inserted into this hemostasis valve, the sealing advantages of the first doughnut-shaped gasket are no longer available because the larger diameter doughnut hole will not seal around the smaller diameter guide wire or catheter. The two gaskets may be provided as separate back-to-back piece parts or as a single piece part, but in either case, are intended to reduce the possibility that blood would escape the hemostasis valve as the tip of the introduced instrument is withdrawn. Thus, the redundancy of the two seals is expected to reduce such leakage.
In still further attempts to accommodate various diameter therapeutic instruments and varying blood pressure between venous and arterial applications, introducers have employed hemostasis valves of the Tuohy-Borst type. For example, U.S. Pat. Nos. 4,726,374 and 4,723,550 provide at least one hemostasis valve assembled within a housing proximal to the side port, where the housing may be tightened down on the resilient gasket material of the valve to compress it to provide a variable pressure seal around the interventional device passing therethrough.
In yet another approach to providing a suitable seal under the varying conditions of usage encountered in practice, it has also been proposed in U.S. Pat. No. 4,917,668 to spring-load the resilient gasket valve member with one or more spring elements to augment the natural resilience of the gasket material.
The hemostasis valves described above all represent departures from and attempts to overcome deficiencies in flat-sided disk-shaped gaskets involving reduced diameter holes, slits and crossed slits therethrough to accommodate instruments passed through the valve housing and sheath, constituting an introducer sheath. It yet remains desirable to provide a simple, easy to manufacture hemostasis valve that is reliable in preventing leakage of blood or air and which possesses a feel of smoothness during insertion and withdrawal of all of the aforementioned varying diameter and material instruments therethrough.